This application focuses on the inflammatory process in the kidney with respect to the roles of the recently recognized family of Junctional Adhesion Molecules (JAMs). Published literature and our preliminary studies reveal that the three family members (JAM1, JAM2 and JAM3) are expressed in normal renal tissue in different but overlapping patterns involving epithelial and endothelial cells. In addition, JAMs are expressed on cells of hematopoietic lineage in different but overlapping patterns. JAM1 is the most studied and anti-JAM1 antibodies have been found to inhibit leukocyte transendothelial migration in vitro and some inflammation in vivo. We have recently found that JAM2 can bind to JAM3 and this interaction is augments adhesion between JAM2 and the beta1 integrin, VLA-4. Our general hypothesis is that JAM family members play significant roles in the inflammatory processes in the kidney, and that each member provides a distinct contribution. Aim 1. Define the adhesive interactions among leukocytes and endothelial cells that involve members of the JAM family (JAM1, 2 and 3). Screening studies in vitro will be performed to determine the ability of blood leukocyte subtypes to adhere to each JAM family member. Follow-up studies for any newly recognized interactions will address mechanisms and functional significance. We will analyze LFA-1 (CD11a/CD18) binding to JAM1, and we will analyze JAM3 binding to JAM2 and the role of VLA-4 (alpha4, beta1). Studies will utilize human cells (leukocytes and endothelial cells) and appropriate probes. Studies will also use cells from knockout mice when these animals become available to confirm the potential mechanisms in that species. Aim 2. Define contributions of JAMs to kidney inflammation. Screening studies in vivo will be performed to determine the distribution of JAM family members in human and murine renal tissue with and without inflammatory disease. We will develop mice with null and conditional knockouts of JAM2 and JAM3, and perform descriptive studies of kidney tissue in comparison to JAM1 knockouts. Two models of inflammation will be evaluated in these knockout mice - anti-glomerular basement membrane nephritis, and chronic obstructive uropathy.